Method and apparatus for transmitting scheduling request signal in mobile communication system

ABSTRACT

A method and an apparatus are provided for receiving a scheduling request in a mobile communication system. Information related to Scheduling Request (SR) transmission resources is transmitted to a User Equipment (UE). An SR is received from the UE. For the received SR, the UE checks whether at least one Buffer Status Report (BSR) is triggered and canceled, and the SR is received if the at least one BSR is triggered and not canceled

PRIORITY

This application is Continuation application of U.S. patent applicationSer. No. 13/499,855, filed in the U.S. Patent and Trademark Office onApr. 2, 2012, which is a National Phase Entry of PCT InternationalApplication No. PCT/KR2010/006950, which was filed on Oct. 11, 2010, andclaims priority to a Korean Patent Application filed in the KoreanIntellectual Property Office on Oct. 9, 2009 and assigned Serial No.10-2009-0096484, the entire disclosures of which are incorporated hereinby reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to scheduling in a mobilecommunication system, and more particularly, to a method and apparatusfor transmitting a scheduling request signal by a User Equipment (UE) ina mobile communication system.

2. Description of the Related Art

Generally, mobile communication systems provide communication serviceswhile securing user mobility. Thanks to technology breakthroughs, themobile communication systems have evolved to provide not only voicecommunication services, but also high-speed data communication services.

Standardization for Long Term Evolution (LTE) in 3^(rd) GenerationPartnership Project (3GPP) is one of the next-generation mobilecommunication systems. LTE is a technology that can implement high-speedpacket-based communication having a maximum data rate of 100 Mbps. Inorder to support this high-speed communication, several methods havebeen discussed, such as a method of reducing the number of nodes in acommunication link by simplifying the network structure, and a method ofapproximating wireless protocols to wireless channels, if possible.

Unlike in voice service, in data service, the amount of wirelessresources allocated to one UE is determined depending on the amount oftransmission data and the channel conditions. Therefore, a wirelesscommunication system, such as the mobile communication system, manages ascheduler to allocate transmission resources taking into account theamount of transmission resources, the channel conditions, and the amountof transmission data. This is performed in the same way in LTE. Ascheduler located in an evolved Node B (eNB) manages wirelesstransmission resources and properly allocates them to UEs.

In the wireless communication system, such as the mobile communicationsystem, data transmission is classified into downlink transmission anduplink transmission depending on the direction of data transmission. Theterm ‘downlink transmission’ refers to transmission from an eNB to a UE,while the term ‘uplink transmission’ refers to transmission from a UE toan eNB.

In the case of downlink transmission, since an eNB may pinpoint thecurrent channel conditions, the amount of allocable wireless resources,and the amount of transmission data, a scheduler in the eNB may smoothlyperform scheduling based on the above information. However, in the caseof uplink transmission, the scheduler in the eNB may not properlyallocate wireless resources to UEs since the uplink transmission may beperformed without scheduler pinpointing the current buffer status ofUEs, causing difficulties in the uplink transmission.

In order to solve the difficulties in the uplink transmission, in theLTE system, a UE reports its current buffer status to an eNB using a‘Buffer Status Report Control Element’.

The ‘Buffer Status Report Control Element’ is set to be transmitted toan eNB by a UE if certain conditions are satisfied, such as, iftransmission data with a high priority is newly generated and if apredetermined timer expires.

A Buffer Status Report (BSR), occurring when new data with a highpriority is generated, may be referred to as a regular BSR. In order totransmit the regular BSR to the eNB as quickly as possible, uponoccurrence of a regular BSR, a UE requests transmission resources forBSR transmission by transmitting 1-bit information calledDedicated-Scheduling Request (D-SR) to the eNB. More specifically, theD-SR is used to request, from the ENB, wireless resources fortransmitting a regular BSR.

SUMMARY OF THE INVENTION

The present invention has been made to address at least the aboveproblems and/or disadvantages and to provide at least the advantagesdescribed below. Accordingly, an aspect of the present inventionprovides a method and apparatus for efficiently transmitting ascheduling request signal by a UE in a mobile communication system.

Another aspect of the present invention provides a method and apparatusfor allowing a UE to be efficiently allocated resources for transmissionof a Buffer Status Report (BSR) in a mobile communication system.

According to one aspect of the present invention, a method is providedfor receiving a scheduling request in a mobile communication system.Information related to Scheduling Request (SR) transmission resources istransmitted to a UE. An SR is received from the UE. For the received SR,the UE checks whether at least one BSR is triggered and canceled, andthe SR is received if the at least one BSR is triggered and notcanceled.

According to another aspect of the present invention, an apparatus isprovided for receiving a scheduling request in a mobile communicationsystem. The apparatus includes a transmitter configured to transmitinformation related to SR transmission resources to a UE. The apparatusalso includes a receiver configured to receive an SR from the UE. Forthe received SR, the UE checks whether at least one BSR is triggered andcanceled, and the SR is received if the at least one BSR is triggeredand not canceled.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of the presentinvention will become more apparent from the following detaileddescription when taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a diagram illustrating a configuration of an LTE mobilecommunication system;

FIG. 2 is a diagram illustrating a structure of a wireless protocol inan LTE system;

FIG. 3 is a diagram illustrating a BSR a D-SR in an LTE mobilecommunication system;

FIG. 4 is a diagram illustrating problems of the conventional technologyrelated to an embodiment of the present invention;

FIG. 5 is a diagram illustrating the transmission of a schedulingrequest signal in a UE, according to an embodiment of the presentinvention;

FIG. 6 is a diagram illustrating problems of the conventional technologyrelated to an embodiment of the present invention, and the transmissionof a scheduling request signal in a UE, according to an embodiment ofthe present invention;

FIG. 7 is a diagram illustrating the transmission of a schedulingrequest signal in a UE, according to an embodiment of the presentinvention; and

FIG. 8 is a block diagram illustrating a UE, according to an embodimentof the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Embodiments of the present invention are described in detail withreference to the accompanying drawings. The same or similar componentsmay be designated by the same or similar reference numerals. Detaileddescriptions of constructions or processes known in the art may beomitted to avoid obscuring the subject matter of the present invention.

Embodiments of the present invention provide a method and apparatus forpreventing a UE from performing unnecessary malfunction in transmittinga D-SR.

FIG. 1 illustrates a configuration of an LTE mobile communicationsystem.

Referring to FIG. 1, a radio access network of the LTE mobilecommunication system includes eNBs or Node Bs 105, 110, 115 and 120, aMobility Management Entity (MME) 125, and a Serving-Gateway (S-GW) 130.A UE 135 accesses the network through the eNB 105 to which it isconnected, and the S-GW 130.

The eNBs 105 to 120 correspond to Node Bs in the legacy UMTS system. TheeNB 105 is connected to the UE 135 over a wireless channel, and plays amore complex role than the legacy Node B. LTE performs scheduling bycollecting status information of UEs, since all user traffic includingreal time services such as Voice over Internet Protocol (VoIP) isserviced over a shared channel. This scheduling function is managed bythe eNBs 105 to 120.

One eNB generally controls a plurality of cells. In order to implement amaximum data rate of 100 Mbps, LTE uses Orthogonal Frequency DivisionMultiplexing (OFDM) in a maximum bandwidth of 20 MHz as a wirelessaccess technology. In addition, LTE applies Adaptive Modulation & Coding(AMC) that adaptively determines a modulation scheme and a channelcoding rate depending on channel conditions of UEs.

The S-GW 130, a device for providing a data bearer, generates or removesa data bearer under control of the MME 125. The MME 125, a deviceresponsible for various control functions for wireless connection, isconnected to a plurality of eNBs.

FIG. 2 illustrates a structure of a wireless protocol in an LTE system.

Referring to FIG. 2, the wireless protocol of the LTE system includesPacket Data Convergence Protocol (PDCP) 205 and 240, Radio Link Control(RLC) 210 and 235, and Medium Access Control (MAC) 215 and 230. The PDCP205 and 240 are responsible for, for example, an operation ofcompressing/decompressing an IP header. The RLC 210 and 235 perform anAutomatic Repeat reQuest (ARQ) operation or the like by reconfiguringPDCP Packet Data Units (PDCP PDUs) into a proper size. The MAC 215 and230 are connected to several RLC-layer devices formed in one UE, andperform an operation of multiplexing RLC PDUs to a MAC PDU, andde-multiplexing a MAC PDU into RLC PDUs. Physical (PHY) layers 220 and225 channel-code and modulate upper layer data into OFDM symbols andtransmit the OFDM symbols over a wireless channel; and/or demodulate andchannel-decode OFDM symbols received over a wireless channel andtransfer the decoded OFDM symbols to their upper layers.

FIG. 3 illustrates a BSR and a D-SR in an LTE mobile communicationsystem.

An eNB 310 may set D-SR transmission resources for a UE 305. The term‘D-SR transmission resources’, as used herein, may refer to resourcesthat an eNB allocates to a UE, allowing the UE to transmit D-SR to theeNB. The D-SR transmission resources may be allocated to the UE 305 bythe eNB 310 for a predetermined period. Accordingly, in step 315, theeNB 310 sends a control message including D-SR transmission resourcesetting information to the UE 305. Based on the control message, the UE305 determines the transmission resources that are set as the D-SRtransmission resources for the UE 305, and the subframe having theavailable D-SR transmission resources.

In step 320, a particular situation is assumed, in which a regular BSRis triggered in the UE 305 at a certain time after step 315. In step325, an SR transmission process is also triggered after the regular BSRis triggered. The term ‘SR transmission process’, as used herein, mayrefer to a process in which a UE transmits a D-SR to an eNB until it isallocated wireless resources for BSR transmission from the eNB. Morespecifically, if the SR transmission process is triggered, the UE 305transmits the D-SR to the eNB 310 until the SR transmission process iscanceled.

Since the UE 305 may determine a subframe allocated to its D-SRtransmission resource based on the control message received in step 315,the UE 305 transmits the D-SR in the allocated subframe. The UE 305repeatedly transmits the D-SR to the eNB 310 until it is allocatedresources for BSR transmission. Assuming that the UE 305 is allocatedresources for BSR transmission in step 345, the UE 305 transmits the BSRto the ENB 310 using the resources for BSR transmission in step 350.

After transmitting the BSR to the eNB 310, the UE 305 cancels the SRtransmission process triggered in step 325, and no longer transmits theD-SR.

However, the eNB 310 may not receive the D-SR that the UE 305transmitted due to, for example, an incorrectly set uplink transmissionpower during the D-SR transmission. In this case, the UE 305 mayinfinitely repeatedly transmit D-SR to the eNB 310, causing an increasein power consumption and uplink interference of the UE 305.

As a solution, the current LTE standard limits the number of UE D-SRtransmissions to a predetermined threshold, dsr-transmax, or as setforth below. If a UE is not allocated resources for BSR transmissionfrom an eNB, even after it transmitted D-SR as many times as thethreshold dsr-transmax, the UE stops the D-SR transmission and starts arandom access process for the BSR transmission.

When the eNB fails to receive an uplink grant even though a UEtransmitted the D-SR to the eNB as many times as the thresholddsr-transmax, i.e., the UE's fails to be allocated resources for BSRtransmission, it suggests a possible fatal error in setting the uplinktransmission for the UE. Therefore, the UE releases dedicated uplinktransmission resources including D-SR transmission resources. When theUE fails to receive an uplink grant from an eNB even though the UEtransmitted the D-SR to the ENB as many times as the thresholddsr-transmax, it is referred to herein as ‘D-SR transmission failure’.

In order to determine whether the D-SR transmission has failed, the UEoperates a predetermined counter in which a parameter SR_COUNTER is set.A value of SR_COUNTER is initialized to 0 if SR is triggered, andincreases by 1 whenever the D-SR is transmitted. If SR_COUNTER arrivesat the threshold dsr-transmax for the D-SR transmission, the UE releasesthe dedicated uplink transmission resources including the D-SRtransmission resources, and performs a random access process,determining that D-SR transmission failure has occurred. A series ofoperations for releasing the dedicated uplink transmission resources,including the D-SR transmission resources, and starting a random accessprocess, is referred to herein as ‘D-SR transmission failure follow-upprocedure’.

In the current LTE standard, after transmitting a (dsr-transmax)-thD-SR, a UE immediately performs the D-SR transmission failure follow-upprocedure without determining whether an uplink grant is received.Specifically, after transmitting the last D-SR, the UE performs the D-SRtransmission failure follow-up procedure before the ENB receives thelast D-SR and allocates an uplink grant. As a result, the UE performsthe D-SR transmission failure follow-up procedure without checking anuplink grant from the ENB for the transmitted last D-SR, so thetransmission of the last D-SR may cause an unnecessary waste ofresources, an increase in uplink interference, and power dissipation ofthe UE. These problems are described in greater detail below, withreference to FIG. 4.

FIG. 4 illustrates problems of the conventional technology related to anembodiment of the present invention.

In FIG. 4, one rectangle represents a 1-msec subframe. Subframes for theD-SR transmission resources, which are allocated to a UE, are shown byarrows 405, 410, 415, 420, and 430.

It is assumed that an SR transmission process is triggered in a UE at anarbitrary time, as shown by reference numeral 435. If the SRtransmission process is triggered in step 435, the UE initializesSR_COUNTER to 0 in step 440, and waits until a subframe allocated foravailable D-SR transmission resources.

In step 445, the UE compares SR_COUNTER with the maximum allowablenumber dsr-transmax of D-SR transmissions in order to determine whetherto perform the D-SR transmission in the subframe 410, which allocated tobe available as D-SR transmission resources. If SR_COUNTER is less thandsr-transmax as a result of the comparison, i.e., if the number of SRtransmissions has not arrived at the maximum allowable number of D-SRtransmissions, the UE increases SR_COUNTER by 1 in step 450, andtransmits the D-SR in step 455.

If the SR transmission process is in progress, the UE repeats anoperation of comparing SR_COUNTER with dsr-transmax in every subframewhere D-SR transmission resources are available, and if SR_COUNTER isless than dsr-transmax, increasing SR_COUNTER by 1 and transmitting theD-SR. For example, if dsr-transmax is set to 3, the UE transmits SR andincreases SR_COUNTER by 1 in a subframe 420 because SR_COUNTER at thetime is 2.

In the next subframe 425, since SR_COUNTER is 3 and a value ofSR_COUNTER is equal to dsr-transmax at this time, the UE performs theD-SR transmission failure follow-up procedure. Specifically, the UEreleases the D-SR transmission resources and performs random access forresources for BSR transmission, if SR_COUNTER is greater than or equalto dsr-transmax. More specifically, the UE performs the D-SRtransmission failure follow-up procedure before the ENB responds to theSR that the UE transmitted in the subframe 420.

This problem occurs because the UE immediately performs the D-SRtransmission failure follow-up procedure in the next subframe after ittransmitted the last D-SR in an operation of the above-describedconventional LTE standard. However, it is preferable that aftertransmitting D-SR, a UE waits for a response thereto from an eNB, i.e.,waits for an uplink grant to be received, for a predetermined period oftime.

An embodiment of the present invention solves the problems describedwith respect to FIG. 4. Conventionally, after transmitting D-SR, a UEincreases SR_COUNTER, compares SR_COUNTER with dsr-transmax, andimmediately performs the D-SR transmission failure follow-up procedureif SR_COUNTER is greater than or equal to dsr-transmax.

However, in an embodiment of the present invention, unlike in theconvention method, a UE increases SR_COUNTER in advance at apredetermined time ahead of the transmission time of the D-SR.Thereafter, the UE compares SR_COUNTER with dsr-transmax, and performsthe D-SR transmission failure follow-up procedure if SR_COUNTER isgreater than dsr-transmax as a result of the comparison. In this way,the embodiment of the present invention may solve the above-describedproblems by changing the start time of the D-SR transmission failurefollow-up procedure.

In accordance with an embodiment of the present invention, a UEtransmits the D-SR but does not start the D-SR transmission failurefollow-up procedure at the time the SR_COUNTER value is equal to thedsr-transmax value. In addition, the UE increases SR_COUNTER by 1 at apredetermined time ahead of the next subframe available for D-SRtransmission resources, satisfying a condition that SR_COUNTER isgreater than dsr-transmax. Thus, the UE may perform the D-SRtransmission failure follow-up procedure without transmitting the D-SR.

As a result, instead of immediately performing the D-SR transmissionfailure follow-up procedure after transmitting the last D-SR, the UEdetermines whether to perform the D-SR transmission failure follow-upprocedure after waiting until the next subframe available for D-SRtransmission resources, preventing unnecessary transmission of the D-SR.

FIG. 5 illustrates an operation of transmitting a scheduling requestsignal in a UE, according to an embodiment of the present invention.

An SR transmission process is triggered due to occurrence of, forexample, a regular BSR, in step 505. The UE initializes SR_COUNTER to 0,in step 510. In step 515, the UE awaits until a predetermined time closeto a subframe available for D-SR transmission resources in order todetermine whether to transmit the D-SR. The predetermined time may beset as a time ahead of a subframe available for D-SR transmissionresources by a UE's processing delay required to determine whether totransmit SR, or whether to perform the D-SR transmission failurefollow-up procedure. This time is subject to change.

In step 520, the UE increases SR_COUNTER by 1 prior to a process ofdetermining whether to transmit the D-SR. By increasing SR_COUNTER inadvance, prior to determining whether to transmit D-SR and whether toperform the D-SR transmission failure follow-up procedure as describedabove, the UE does not unnecessarily transmit the D-SR before performingthe D-SR transmission failure follow-up procedure.

For example, in FIG. 4, the UE updates SR_COUNTER to 4 and comparesSR_COUNTER with dsr-transmax at a predetermined time, which precedes thesubframe 430 and is close to the subframe 430. The UE performs thefollow-up operation in the subframe 430 because SR_COUNTER is greaterthan dsr-transmax. Specifically, instead of immediately performing thefollow-up operation after transmitting the last D-SR, the UE performsthe follow-up operation after waiting until the subframe time availablefor D-SR transmission resources.

In step 525, the UE compares SR_COUNTER with dsr-transmax. If SR_COUNTERis less than or equal to dsr-transmax, the UE proceeds to step 545 forD-SR transmission. If SR_COUNTER is greater than dsr-transmax, the UEproceeds to step 530 for D-SR transmission failure follow-up procedure.

Conventionally, the UE performs the operation of step 530 if SR_COUNTERis greater than or equal to dsr-transmax. However, in an embodiment ofthe present invention, the UE proceeds to step 530 if SR_COUNTER isgreater than dsr-transmax. If dsr-transmax is set to a value which isgreater by 1 than the conventional technology, the conventionaldetermination procedure may be used. Specifically, in this case, ifSR_COUNTER is less than dsr-transmax in step 525, the UE proceeds tostep 545. If SR_COUNTER is equal to or greater than dsr-transmax, the UEmay proceeds to step 530. In this case, however, the UE should setdsr-transmax to a value which is greater by 1 than the conventionalmethod, because (dsr-transmax-1)-th D-SR transmission is the last D-SRtransmission.

Proceeding to step 530 means that even though the UE has performed D-SRtransmission a predetermined maximum number of D-SR transmissions, theUE has failed to receive a response thereto, i.e., an uplink grant.Thus, the UE performs the D-SR transmission failure follow-up procedure.The UE releases various dedicated uplink transmission resourcesincluding D-SR transmission resources in step 530, starts a randomaccess process in step 535, and cancels the entire ongoing SRtransmission process in step 540.

Proceeding to step 545 means that the number of D-SR transmissions hasnot reached a predetermined maximum number of D-SR transmissions, so theUE transmits the D-SR. In step 550, the UE checks whether the SRtransmission process is in progress. When the SR transmission process isin progress, the SR transmission process has not been canceled afterbeing triggered. The SR transmission process may be canceled by the D-SRtransmission failure follow-up procedure, as in step 540, and may becanceled when a regular BSR is transmitted.

If the SR transmission process is still in progress, the UE returns tostep 515 and continues to perform the SR transmission process. However,if the SR transmission process is not in progress, i.e., if the SRtransmission process has been canceled when the BSR is transmitted afterthe SR transmission process was triggered, the UE terminates the SRtransmission process in step 555.

FIG. 6 is a diagram illustrating a process of transmitting a schedulingrequest signal in a UE, according to an embodiment of the presentinvention.

FIG. 6 illustrates problems of the conventional technology related to anembodiment of the present invention, and a process of transmitting ascheduling request signal in a UE, according to an embodiment of thepresent invention.

As described above, if a regular BSR is triggered, an SR transmissionprocess is also triggered in order for the UE to be allocated resourcesfor transmission of the regular BSR. However, exceptional situations mayoccur, in which, even though a regular BSR is triggered, the D-SR is nottransmitted.

For example, when a regular BSR is triggered and an SR transmissionprocess is triggered at an arbitrary time in step 605, and the D-SR istransmitted in a subframe available for D-SR transmission resources instep 610, if the D-SR has been successfully transmitted and received,the UE receives an uplink grant in an arbitrary subframe in step 615. Instep 625, the UE performs uplink transmission 4 subframes after thesubframe where the uplink grant was received.

Upon receiving the uplink grant, the UE generates a MAC PDU to besubject to uplink transmission, and the MAC PDU includes the BSR. It isassumed that a new regular BSR is generated in step 635, between a time620 where the generation of MAC PDU is completed and a time of step 625where the generated MAC PDU is actually transmitted.

The new regular BSR may not be included in the MAC PDU transmitted atthe time of step 625. However, if the MAC PDU with the BSR istransmitted at the time of step 625, the SR transmission processtriggered in step 605 is canceled at a time of step 630. The SRtransmission process for the regular BSR newly generated in step 635 maybe canceled without the start of the D-SR transmission.

To solve the above problems, the current LTE standard provides that theexisting SR transmission process is canceled only when BSR reflectingthe latest buffer status is transmitted. This solution allows the UE toaccess an eNB with the SR transmission process for the regular BSR newlygenerated in step 635, without canceling the SR transmission processtriggered in step 605 for the previous BSR in the situation described inconjunction with FIG. 6. Therefore, the SR_COUNTER used in the SRtransmission process for the previous BSR in step 605 is used as is,with the SR_COUNTER value not initialized. This may cause too earlyexecution of the D-SR transmission failure follow-up procedure becauseof a reduction in the maximum allowable number of D-SR transmissions fora new BSR, in step 635.

In order to solve this problem, in an embodiment of the presentinvention, the UE cancels the current ongoing SR transmission process(i.e., SR transmission process of step 605 in FIG. 6) at a moment thatMAC PDU containing BSR is transmitted, and triggers a new SRtransmission process if there is no current ongoing SR transmissionprocess, even though a new regular BSR was triggered.

For example, the UE cancels the ongoing SR transmission process at thetime of step 630, if it transmits the MAC PDU containing the BSR. The UEtriggers a new SR transmission process, if there is no current ongoingSR transmission process even though there is the BSR (i.e., the BSR instep 635), which is not canceled at the time of step 630. Specifically,in step 635, the UE newly triggers an SR transmission process fortransmission of a newly generated regular BSR after canceling theexisting SR transmission process of step 630.

FIG. 7 illustrates an operation of transmitting a scheduling requestsignal in a UE, according to an embodiment of the present invention.

A regular BSR is triggered in step 705. The UE triggers an SRtransmission process, in step 710. Specifically, the UE transmits theD-SR at a time when SR transmission resources are available. Uponreceiving an uplink grant, the UE generates and transmits the MAC PDUincluding the BSR. Upon failure to receive an uplink grant, the UEperforms an operation such as transmitting the D-SR.

While performing the operation, the UE determines whether the triggeredBSR is canceled, in step 715. For example, the UE may monitor whetherthe triggered BSR is not canceled, in every Transmission Time Interval(TTI). After the BSR is triggered, if the BSR, in which the latestbuffer status is reflected, is included in the MAC PDU (to betransmitted), the triggered BSR process is terminated. If the triggeredBSR is canceled, the UE terminates the operation.

On the other hand, if the triggered BSR is not canceled, the UEdetermines whether there is a current ongoing SR transmission process,in step 720. For reference, the triggered BSR process is not canceled,if the BSR, in which the latest buffer status is reflected, is notincluded in MAC PDU yet, or if BSR does not reflect the current bufferstatus of the UE even though the BSR is included in MAC PDU.

In the general case, if there is a non-canceled BSR, an ongoing SRtransmission process should also exist. However, if an SR transmissionprocess is canceled while the BSR, in which the previous buffer statusis reflected, is transmitted, as in the operation of steps 625 and 630,there may be no ongoing SR transmission process even though there is anon-canceled BSR.

Therefore, if there is a current ongoing SR transmission process, the UEreturns to step 715 and continuously monitors whether the BSR process iscanceled while continuing to perform the SR transmission process.However, if there is no current ongoing SR transmission process, the UEtriggers a new SR transmission process in step 725. Thereafter, the UEreturns to step 715 and monitors whether the BSR is canceled. If the BSRis canceled in step 715, the UE terminates the operation.

FIG. 8 is a block diagram of a UE, according to an embodiment of thepresent invention.

It should be noted that in the UE's block diagram of FIG. 8, its upperlayer device is not shown.

Referring to FIG. 8, the UE includes a multiplexing/demultiplexing(MUX/DEMUX) unit 805, an HARQ processor 810, an SR/BSR controller 815, aMAC controller 820, and a transceiver 825.

The SR/BSR controller 815 determines whether the BSR is triggered bymonitoring the occurrence of upper layer data. In accordance with anembodiment of the present invention illustrated in FIG. 5, if the BSR istriggered, the SR/BSR controller 815 triggers an SR transmissionprocess, determines whether to transmit the D-SR and whether to performthe D-SR transmission failure follow-up procedure by operatingSR_COUNTER and dsr-transmax, and controls the transceiver 825 totransmit D-SR or perform a random access operation based on thedetermination results. In accordance with an embodiment of the presentinvention illustrated in FIG. 7, the SR/BSR controller 815 determineswhether the BSR is canceled, and triggers a new SR transmission processif there is no ongoing SR transmission process even though there is anon-canceled BSR.

The MAC controller 820 analyzes scheduling information received overdownlink and uplink control channels, and controls the transceiver 825to receive downlink data or transmit uplink data.

The MAC controller 820 controls the MUX/DEMUX unit 805 to generateuplink transmission data. Upon receiving an uplink grant, the MACcontroller 820 notifies the SR/BSR controller 815 of the receipt of theuplink grant so that the SR/BSR controller 815 may determine whether anSR transmission process is canceled and whether the BSR is canceled.

The transceiver 825 is a device for transmitting/receiving the MAC PDUsor control information, and HARQ packets over wireless channels. TheHARQ processor 810 is a set of soft buffers configured to perform anHARQ operation, and is identified with an HARQ process identifier.

The MUX/DEMUX unit 805 configures MAC PDUs by concatenating data carriedon a plurality of logical channels, or demultiplexes MAC PDUs into MACSDUs and delivers them over a proper logical channel.

While the invention has been shown and described with reference tocertain embodiments thereof, it will be understood by those skilled inthe art that various changes in form and detail may be made thereinwithout departing from the spirit and scope of the invention as definedby the appended claims.

What is claimed is:
 1. A method for receiving a scheduling request in amobile communication system, the method comprising: transmittinginformation related to Scheduling Request (SR) transmission resources toa User Equipment (UE); and receiving an SR from the UE, wherein for thereceived SR, the UE checks whether at least one Buffer Status Report(BSR) is triggered and canceled, and the SR is received if the at leastone BSR is triggered and not canceled.
 2. The method of claim 1,wherein: the at least one BSR is a regular BSR; and the SR is receivedif the at least one regular BSR is triggered and not canceled.
 3. Themethod of claim 1, further comprising receiving a Medium Access Control(MAC) Packet Data Unit (PDU) including the at least one BSR from the UE;wherein the SR is not received, if the MAC PDU is received.
 4. Themethod of claim 2, wherein the regular BSR is triggered if data becomesavailable for uplink transmission with high priority.
 5. The method ofclaim 1, wherein a random access process is initiated if a number of SRtransmissions by the UE is equal to a maximum number of SRtransmissions.
 6. The method of claim 1, wherein the SR is not received,if a random access process is initiated before the SR is received. 7.The method of claim 1, wherein uplink transmission resources arereleased if a number of SR transmissions by the UE is equal to a maximumvalue.
 8. The method of claim 7, wherein the number of SR transmissionsby the UE is set to zero (0), if there is no other pending SR and the SRis triggered.
 9. The method of claim 1, wherein whether the BSR iscanceled is checked in every Transmission Time Interval (TTI).
 10. Anapparatus for receiving a scheduling request in a mobile communicationsystem, the apparatus comprising: a transmitter configured to transmitinformation related to Scheduling Request (SR) transmission resources toa User Equipment (UE); and a receiver configured to receive an SR fromthe UE; wherein for the received SR, the UE checks whether at least oneBuffer Status Report (BSR) is triggered and canceled, and the SR isreceived if the at least one BSR is triggered and not canceled.
 11. Theapparatus of claim 10, wherein the at least one BSR is a regular BSR,and the receiver receives the SR, if the regular BSR is triggered andnot canceled.
 12. The apparatus of claim 10, wherein the receiverreceives a Medium Access Control (MAC) Packet Data Unit (PDU) includingthe at least one BSR from the UE, and does not receive the SR.
 13. Theapparatus of claim 11, wherein the regular BSR is triggered if databecomes available for uplink transmission with a high priority.
 14. Theapparatus of claim 10, wherein a random access process is started if anumber of SR transmissions by the UE is equal to a maximum number of SRtransmissions.
 15. The apparatus of claim 10, wherein the receiver doesnot receive the SR, if a random access process is initiated before theSR is received.
 16. The apparatus of claim 10, wherein uplinktransmission resources are released if a number of SR transmissions bythe UE is equal to a maximum value.
 17. The apparatus of claim 16,wherein the number of SR transmissions by the UE is set to zero (0), ifthere is no other pending SR and the SR is triggered.
 18. The apparatusof claim 10, wherein whether the BSR is canceled is checked in everyTransmission Time Interval (TTI).